use vstd::prelude::*; fn main() {} verus! { pub struct Solution; pub open spec fn value_occurs(permutation: Seq, value: int) -> bool { exists|pos: int| 0 <= pos < permutation.len() && permutation[pos] == value } pub open spec fn all_values_occur(permutation: Seq) -> bool { forall|value: int| 1 <= value <= permutation.len() ==> #[trigger] value_occurs(permutation, value) } pub open spec fn is_valid_permutation(permutation: Seq) -> bool { 1 <= permutation.len() <= 100_000 && forall|i: int| 0 <= i < permutation.len() ==> 1 <= #[trigger] permutation[i] <= permutation.len() && forall|i: int, j: int| 0 <= i < j < permutation.len() ==> permutation[i] != permutation[j] && all_values_occur(permutation) } pub open spec fn are_valid_queries(queries: Seq, n: int) -> bool { 1 <= queries.len() <= 100_000 && forall|i: int| 0 <= i < queries.len() ==> 1 <= #[trigger] queries[i] <= n } pub open spec fn position_of(permutation: Seq, value: int) -> int recommends is_valid_permutation(permutation), 1 <= value <= permutation.len(), { choose|pos: int| 0 <= pos < permutation.len() && permutation[pos] == value } pub open spec fn total_vasya(permutation: Seq, queries: Seq, k: int) -> int recommends is_valid_permutation(permutation), are_valid_queries(queries, permutation.len() as int), 0 <= k <= queries.len(), decreases k, { if k <= 0 { 0 } else { total_vasya(permutation, queries, k - 1) + position_of(permutation, queries[k - 1] as int) + 1 } } pub open spec fn total_petya(permutation: Seq, queries: Seq, k: int) -> int recommends is_valid_permutation(permutation), are_valid_queries(queries, permutation.len() as int), 0 <= k <= queries.len(), decreases k, { if k <= 0 { 0 } else { total_petya(permutation, queries, k - 1) + permutation.len() - position_of(permutation, queries[k - 1] as int) } } impl Solution { pub fn effective_approach(permutation: Vec, queries: Vec) -> (result: (i64, i64)) requires is_valid_permutation(permutation@), all_values_occur(permutation@), are_valid_queries(queries@, permutation.len() as int), ensures result.0 as int == total_vasya(permutation@, queries@, queries.len() as int), result.1 as int == total_petya(permutation@, queries@, queries.len() as int), { let n = permutation.len(); let mut positions = Vec::new(); let mut t = 0usize; while t <= n { positions.push(0i64); t += 1; } let mut i = 0usize; while i < n { let value = permutation[i] as usize; positions.set(value, i as i64 + 1); i += 1; } let mut vasya = 0i64; let mut petya = 0i64; let mut j = 0usize; while j < queries.len() { let value = queries[j] as usize; let p = positions[value]; vasya += p; petya += n as i64 - p + 1; j += 1; } (vasya, petya) } } }